package com.hmdp.service.impl;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.fasterxml.jackson.databind.ser.std.RawSerializer;
import com.hmdp.dto.Result;
import com.hmdp.entity.Shop;
import com.hmdp.mapper.ShopMapper;
import com.hmdp.service.IShopService;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.hmdp.utils.CacheClient;
import com.hmdp.utils.RedisData;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import javax.annotation.Resource;

import java.time.LocalDateTime;
import java.util.concurrent.Executor;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;

import static com.hmdp.utils.RedisConstants.*;

/**
 * <p>
 *  服务实现类
 * </p>
 *
 * @author 虎哥
 * @since 2021-12-22
 */
@Service
public class ShopServiceImpl extends ServiceImpl<ShopMapper, Shop> implements IShopService {

    @Resource
    private StringRedisTemplate stringRedisTemplate;
    @Resource
    private CacheClient cacheClient;

    @Override
    public Result queryShopById(Long id) {
        // 缓存穿透
        //Shop shop = queryWithPassThrough(id);
        //Shop shop = cacheClient.queryWithPassThrough(CACHE_SHOP_KEY, id, Shop.class, this::getById, CACHE_SHOP_TTL, TimeUnit.MINUTES);

        // 缓存击穿--- 互斥锁
        //Shop shop = queryWithMutex(id);

        // 缓存穿透--逻辑过期
        // Shop shop = queryWithLogicalExpire(id);
        Shop shop = cacheClient.queryWithLogicalExpire(CACHE_SHOP_KEY, id, Shop.class, this::getById, 20L, TimeUnit.SECONDS);

        if (shop == null) {
            return Result.fail("店铺信息不存在！！！");
        }
        return Result.ok(shop);
    }

    // 线程池
    private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);

    // 缓存穿透--逻辑过期
    /*
    public Shop queryWithLogicalExpire(Long id){
        // 1、从 redis 查询商铺缓存
        String key = CACHE_SHOP_KEY + id;
        String shopJson = stringRedisTemplate.opsForValue().get(key);
        // 2、判断是否存在
        if (StrUtil.isBlank(shopJson)) {
            // 3、存在，直接返回
            return null;
        }
        // 4、命中，需要先把 json 反序列化为对象
        RedisData redisData = JSONUtil.toBean(shopJson, RedisData.class);
        JSONObject data = (JSONObject) redisData.getData();
        Shop shop = JSONUtil.toBean(data, Shop.class);
        LocalDateTime expireTime = redisData.getExpireTime();
        // 5、判断是否过期
        if (expireTime.isAfter(LocalDateTime.now())) {
            // 5.1 未过期，直接返回店铺信息
            return shop;
        }
        // 5.2 已过期，需要缓存重建
        // 6、缓存重建
        // 6.1 获取互斥锁
        String lockKey =LOCK_SHOP_KEY + id;
        boolean isLock = tryLock(lockKey);
        // 6.2 判断是否获取锁成功
        if (isLock) {
            // 6.3 成功，开启独立线程，实现缓存重建
            CACHE_REBUILD_EXECUTOR.submit(() ->{
                try {
                    // 重建缓存
                    this.saveShop2Redis(id, 20L);
                }catch (Exception e) {
                    throw new RuntimeException(e);
                }finally {
                    // 释放锁
                    unLock(lockKey);
                }
            });
        }
        // 6.4 返回过期时间的商铺信息
        return shop;
    }
     */

    // 缓存击穿的方法
    /*
    public Shop queryWithMutex(Long id){
        // 1、从 redis 查询商铺缓存
        String key = CACHE_SHOP_KEY + id;
        String shopJson = stringRedisTemplate.opsForValue().get(key);
        // 2、判断是否存在
        if (StrUtil.isNotEmpty(shopJson)) {
            // 3、存在，直接返回
            Shop shop = JSONUtil.toBean(shopJson, Shop.class);
            return shop;
        }
        //  判断命中是否未空值
        if (shopJson != null) {
            // 返回错误信息
            return null;
        }

        // 4、实现缓存重建
        // 4.1 、获取互斥锁
        String lockKey = "lock:shop:" + id;
        Shop shop = null;
        try {
            boolean isLock = tryLock(lockKey);
            // 4.2 、判断是否获取成功
            if(!isLock){
                // 4.3 、失败，则休眠重试
                Thread.sleep(50);
                return queryWithMutex(id);
            }
            // 4.4 、成功，根据 id 查询数据库
            shop = getById(id);
            // 模拟重建延时
            Thread.sleep(200);
            // 5、不存在，返回错误
            if (shop == null) {
                // 将空值写入 redis
                stringRedisTemplate.opsForValue().set(key, "", CACHE_NULL_TTL , TimeUnit.MINUTES);
                // 返回错误信息
                return null;
            }
            // 6、存在，写入 redis
            stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(shop), CACHE_SHOP_TTL , TimeUnit.MINUTES);
        } catch (InterruptedException e){
            throw new RuntimeException(e);
        } finally {
            // 7、释放互斥锁
            unLock(lockKey);
        }
        // 8、返回
        return shop;
    }
     */

    // 缓存穿透--互斥锁的方法
    /*
    public Shop queryWithPassThrough(Long id){
        // 1、从 redis 查询商铺缓存
        String key = CACHE_SHOP_KEY + id;
        String shopJson = stringRedisTemplate.opsForValue().get(key);
        // 2、判断是否存在
        if (StrUtil.isNotEmpty(shopJson)) {
            // 3、存在，直接返回
            Shop shop = JSONUtil.toBean(shopJson, Shop.class);
            return shop;
        }
        //  判断命中是否未空值
        if (shopJson != null) {
            // 返回错误信息
            return null;
        }
        // 4、不存在，根据 id 查询数据库
        Shop shop = getById(id);
        // 5、不存在，返回错误
        if (shop == null) {
            // 将空值写入 redis
            stringRedisTemplate.opsForValue().set(key, "", CACHE_NULL_TTL , TimeUnit.MINUTES);
            // 返回错误信息
            return null;
        }
        // 6、存在，写入 redis
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(shop), CACHE_SHOP_TTL , TimeUnit.MINUTES);
        return shop;
    }
     */

    // 缓存击穿-获取锁
    /*
    private boolean tryLock(String key){
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);
    }
     */

    //  缓存击穿-释放锁
    /*
    private void unLock(String key){
        stringRedisTemplate.delete(key);
    }
     */

    // 缓存击穿-逻辑过期
    public void saveShop2Redis(Long id, Long expireSeconds) throws InterruptedException {
        // 1、查询店铺数据
        Shop shop = getById(id);
        Thread.sleep(200);
        // 2、封装过期时间
        RedisData redisData = new RedisData();
        redisData.setData(shop);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(expireSeconds));
        // 3、写入 redis
        stringRedisTemplate.opsForValue().set(CACHE_SHOP_KEY + id, JSONUtil.toJsonStr(redisData));
    }

    @Override
    @Transactional
    public Result updateShop(Shop shop) {
        Long id = shop.getId();
        if (id == null) {
            return Result.fail("店铺 id 不能为空!");
        }
        // 1、更新数据库
        updateById(shop);
        // 2、删除缓存
        stringRedisTemplate.delete(CACHE_SHOP_KEY + id);

        return Result.ok();
    }
}
